1. Field
One or more embodiments relate to methods of measuring a frequency of a coordinate indicating device, and electronic apparatuses thereof, and more particularly, to methods of measuring a frequency of an electromagnetic signal generated by a coordinate indicating device, in order to sense a pen pressure of the coordinate indicating device on a sensor pad receiving the electromagnetic signal generated by the coordinate indicating device, and electronic apparatuses thereof.
2. Description of the Related Art
Various electronic apparatuses configured to output/input data from/to a touch screen through a touch pad have been developed.
An electronic apparatus includes a touch pad coupled with a display panel and senses a touch or access of a user or pen through the touch pad to receive an input of data. A method of inputting data to a display screen through the touch pad may be referred to as a touch screen input method.
A touch screen input method has been used to enable a user to input data to an electronic apparatus such as a portable computer such as a notebook computer, a netbook computer, or a tablet personal computer (PC); a portable terminal such as a smart phone, a portable multimedia player (PMP), or a personal digital assistant (PDA); or a smart television (TV).
The touch screen input method enables the user to input data to the electronic apparatus by touching a predetermined point on a display screen of the electronic apparatus, e.g., even without using an additional input/output unit such as a keyboard or a mouse. A user may directly perform a handwriting input or a graphic operation on the touch screen by using a coordinate indicating device. Thus, the electronic apparatus using the touch screen input method may provide an interface that increases the user's convenience.
The touch screen input method may be classified into a resistive method, an electrostatic method, or an electromagnetic resonance (EMR) method (or an electromagnetic method), depending on the method of detecting a point indicated by the user, for example, a touch point of the coordinate indicating device.
The resistive method senses a pressed point according to a current change when a voltage is applied, and senses that two conductive layers disposed on a screen are touched by a user or by a coordinate indicating device. The capacitive method senses a touch based on capacitance coupling. The EMR method senses a pen pressure and coordinate information of a coordinate indicating device by using a sensing panel including an array of electrodes and analyzing a phenomenon in which a coil installed in the coordinate indicating device stores and then returns energy in response to a specific frequency emitted from the sensing panel.
The EMR method may quickly and accurately implement a handwriting input of a user when the user writes on a touch screen by hand by using a coordinate indicating device.
In the EMR method, a pen pressure of the coordinate indicating device is related to a resonance frequency. In general, a pen pressure sensing circuit includes a variable capacitor or a variable inductor, and a resonance frequency changes when a capacitance value or an inductance value changes according to the level of pressure applied to a pen tip. Therefore, to accurately measure the pen pressure, it is necessary to provide an electronic apparatus and a method that may accurately measure a frequency of an electromagnetic signal emitted from the coordinate indicating device.